THIS INVENTION relates to a deep-level mine conveyance system. It also relates to a method of reducing tension in a cable of a deep-level mine shaft conveyance system.
Traditional conveyance systems, such as cable hoisting arrangements used in mining operations, typically include a drive or winding mechanism which operatively hoists a skip or cage via a rope or cable. The drive mechanism is normally surface mounted and the cage and its load are supported by the rope and, accordingly, in order to hoist heavy loads from a substantial depth a rope with a large cross-sectional area is required. The large cross-sectional area results in a heavier rope resulting in further disadvantages, e.g a restriction in the maximum depth from which the load can be hoisted. Linear conveyance systems which include linear synchronous motors are disclosed in JP 09 142742 A (TODA CONSTR CO LTD), JP 01 220691 (MITSUBISHI ELECTRIC CORP), U.S. Pat. No. 5,195,615 A (MANNING MICHAEL J N) and EP 0 254 840 A (GEBAUER AG). It is however to be noted that these inventions use friction winders which operate on a counterweight principle in dual shaft configuration and are generally not suitable for deep-level mining operations i.e. for mine shafts deeper than about 1500 m.
According to the invention, there is provided a deep-level mine shaft conveyance system which includes,
a conveyance for conveying cargo;
a linear motor including a guide member carrying stator windings, the guide member being mounted in use in a mine shaft in its lower end region which is at a depth in excess of 1500 m, and a reaction member mounted to the conveyance for displacement along the guide member by electromagnetic forces;
a hoisting cable in excess of 1500 m in length and anchored at its lower end to the conveyance;
electrical winding means including a drum, the hoisting cable being anchored at its upper end to the drum and being wound and unwound around the drum to displace the conveyance along the mine shaft, the linear motor at least assisting displacement of the conveyance in the lower end region.
The system may include two linear motors, reaction members of the linear motors being mounted on opposed sides of the conveyance and guide rails carrying stator windings associated with the reaction members being provided in use on opposed sides of the mine shaft.
Typically, the conveyance is shaped and dimensioned to convey personnel in underground mining operations and includes mounting means for mounting the winding means proximate a ground surface of the mine shaft and mounting the guide means along a mine shaft. The winding means is typically configured for operation in single shaft deep mining applications.
The conveyance and/or the guide means and/or the winding means are typically substantially similar to a conventional drum hoisting arrangement used in mining operations. Likewise, the linear motor may be a linear synchronous motor arranged in a conventional fashion.
The guide means are typically in the form of guide rails which extend substantially vertically, when installed, at least along the lower end region of the mine shaft. The linear motor is preferably mounted along a lower end region of the guide rails.
The system typically includes a controller for controlling operation of the linear motor and the winding means. Typically, the controller is operable to disable the linear motor when the conveyance is above a predetermined position along the guide means, typically the position is between about 75% to about 80% down the mine shaft. When the conveyance is below the predetermined position, the controller may be operable to enable the linear motor and control operation of the winding means to reduce tension in the cable. In certain embodiments, the controller is operable to support the conveyance and its load in such a fashion so that it is partially supported by both the linear motor and the cable hoisting arrangement.
Preferably, the controller is arranged to activate the linear motor at least to assist in braking the conveyance at substantial depth, accelerating the conveyance at substantial depth, or the like.
The linear motor may include a primary winding arrangement mounted along the guide means, and a secondary magnet arrangement mounted to the conveyance, which is typically a lift cage or the like.
Further in accordance with the invention, there is provided a method of reducing tension in a cable of a deep-level mine shaft conveyance system which includes electrical winding means to which the cable is anchored, the method including activating a linear motor mounted to guide rails and to a conveyance of the system at least partially to inhibit downward displacement of the conveyance and thereby reduce the tension in the cable.